1. Field of the Invention
The present invention relates to a vehicle-mounted electrical component connected between a prescribed power source and a plurality of loads for detecting a break in each load by detecting voltage drop at each individual resistance connected between each load and the power source by each voltage detector.
2. Description of the Related Art
In a combination vehicle-mounted electronic unit/rear junction block (rear J/B) for detecting a break in the high-mount stop lamp, the stop lamp, and the tail lamp of the vehicle, a break in the lamp has been detected, as shown in FIG. 15 (related example 1), by connecting detector resistances 4a-4i to the lamps 1a, 2a-2d, 3a-3d respectively in series in the rear junction block JB1 (rear J/B A), and then connecting voltage detectors 5a-5i to the detector resistances 4a-4i respectively in parallel with respect to each other so that voltage drop, if any, at any of the detector resistance 4a-4i is detected by the corresponding voltage detector when the lamps 1a, 2a-2d, 3a-3d are energized. Each voltage detector 5a-5i is constructed in such a manner that the electric potential difference generated across the detector resistance 4a-4i is supplied as voltage when the detector resistance 4a-4i is energized, and a prescribed signal is determined by the external determination apparatus, not shown, with said voltage as a power source. More specifically, a low voltage output is produced by the use of the voltage drop at each detector resistance 4a-4i while each detector resistance 4a-4i is being energized, and a high voltage output is produced by maintaining the voltage level of the power source 10 when each detector resistance 4a-4i is not energized.
In the electronic unit described above, in many cases, the numbers of high-mount stop lamps 1a, of stop lamps 2a-2d and of tail lamps 3a-3d installed are different depending on the grade or type of the automotive vehicle. For example, in the related example 1 shown in FIG. 15, a high-mount stop lamp 1a with power consumption of 18 watts, four stop lamps 2a-2d with power consumption of 21 watts, and four tail lamps 3a-3d with power consumption of 5 watts are provided, and in the related example 2 shown in FIG. 16, a rear junction block JB2 (rear J/B B) comprises two high-mount stop lamps 1a, 1b, two stop lamps 2a, 2b, and two tail lamps 3a, 3b. There is also another example having two stop lamps, two high-mount stop lamps, and four tail lamps though it is not shown in the figure. The numbers of the lamps 1a, 1b, 2a-2d, 3a-3d in the first, second, and another examples of the related art are shown in Table 1 below.
Reference numerals 6 and 7 in FIGS. 15 and 16 designate ON-OFF switches, and reference numerals 8 and 9 designate fuses respectively.
In the rear junction block JB1 of the related example 1 shown in FIG. 15, the first resistance 4a and the first voltage detector 5a are assigned to a single high-mount stop lamp 1a, the second resistance 4b and the second voltage detector 5b are assigned to the first stop lamp 2a, the third resistance 4c and the third voltage detector 5c are assigned to the second stop lamp 2b, the fourth resistance 4d and the fourth voltage detector 5d are assigned to the third stop lamp 2c, the fifth resistance 4e and the fifth voltage detector 5e are assigned to the fourth stop lamp 2d, the sixth resistance 4f and the sixth voltage detector 5f are assigned to the first tail lamp 3a, the seventh resistance 4g and the seventh voltage detector 5g are assigned to the second tail lamp 3b, the eighth resistance 4h and the eighth voltage detector 5h are assigned to the third tail lamp 3c, and the ninth resistance 4i and the ninth voltage detector 5i are assigned to the fourth tail lamp 3d and connected respectively.
When the junction block JB 2 having the same structure as the rear junction block JB1 of the related example 1 shown in FIG. 15 is applied to the automotive vehicle of the related example 2 shown in FIG. 16, the resistances 4d, 4e and the voltage detectors 5d, 5e for the two stop lamps 2c, and the resistances 4h, 4i and the voltage detectors 5h, 5i for the second tail lamps 3c, 3d for two tail lamps 3c, 3d of the related example 1 are redundant in the related example 2, when assignments of the related example 1 are maintained since the number of the lamps installed in the related example 1 and the number of the lamps installed in the related example 2 are different as shown in Table 1. In addition, the resistance and the voltage detector for the second high-mount stop lamp 1b in the related example 2 are not provided in the rear junction block JB1 of the related example 1, thereby resulting in shortage of circuit components.
In this case, since the load for the stop lamps 2a-2d with the power consumption of 21 watts and that for the high-mount stop lamp 1a, 1b with the power consumption of 18 W are generally equal, the identical components are used for each voltage detector 4a-4e in the real junction block JB1. Therefore, in the related example 2 shown in FIG. 16, one of the resistances 4d, 4e and the voltage detectors 5d, 53 for the redundant lamps (the resistance 4d and the voltage detecting circuit 5d) may be used for the second high-mount stop lamp 1b to supplement the shortage of the resistance and the voltage detector for the second high-mount stop lamp 1b. 
However, in the related example 2 of FIG. 16, the resistances 4e, 4h, 4i and the voltage detectors 5e, 5h, 5i are still redundant. In such a case, when no lamp is connected to these resistances 4e, 4h, 4i and the voltage detectors 5e, 5h, 5i as a load, each voltage detector 5e, 5h, 5i outputs high voltage since the resistances 4e, 4h, 4i are not energized and thus no voltage drop has occurred. As a result, each voltage detector 5e, 5h, 5i makes a false detection that the lamp is broken, and may make a false alarm by a prescribed alarm apparatus (not shown).
Therefore, it is desired that the redundant resistances 4e, 4h, 4i and the voltage detectors 5e, 5h, 5i be connected to a prescribed external circuit so as not to be detected as a break. However, the method of providing such an external circuit to cause a short-circuit on the ground may results in deterioration of the detector resistances 4e, 4h, 4i because of excessive current flows therethrough. In addition, even when they are short-circuited on the side of the power source, the voltage detector 5e, 5h, 5i may detect a break in error. Therefore, a countermeasure against a false detection by the use of the external circuit is very difficult and ineffective because it is required to flow a current corresponding to the load of each respective lamp 2a-2d, 3a-3d. Therefore, other specific rear junction blocks (rear J/B, B and rear J/B C) in which the redundant resistances and the voltage detectors are eliminated must be provided according to the number of the lamp installed.
Under such a circumstance, the product number increases, and thus much effort is required for establishing new product numbers, and control of the product numbers in the process of manufacturing the rear junction block becomes complicated. In addition, support for establishment of the new product number for the limited-edition car results in increase in the number of manufacturing processes and much difficulty in maintenance.
Accordingly, it is an object of the present invention to provide a general-purpose vehicle-mounted electrical component adaptable for any cars irrespective of the grade or differences of models and types.
In order to achieve the above object, according to a first aspect of the invention, there is provided a vehicle-mounted electrical component to be connected between a prescribed power source and a plurality of loads, comprising a main body of the vehicle-mounted electrical component, a plurality of resistances positioned within said body and connected between said each individual load and said power source, a voltage detector positioned in said body for detecting a break in said each load by detecting voltage drop at each resistance individually, a potentially redundant resistance connecting terminal to be connected to at least said detector resistance and said voltage detector that can be redundant depending on the number of said load installed thereto out of said detector resistances and said voltage detectors, and an intermediate connecting terminal connected to the power source connecting terminal to be connected to said power source, and each assigned to said each individual potentially redundant resistance connecting terminal, wherein said potentially redundant resistance connecting terminal and said intermediate connecting terminal are formed in parallel with respect to each other exposed on the external surface of the main body of said vehicle-mounted electrical component so that they can be short-circuited with respect to each other by the prescribed external connecting member.
For example, said connecting member used is an electrically conductive short-circuit member detachably connectable to said potential redundancy resistance connecting terminal and to said intermediate connecting terminal on the external surface of said main body, according to the second aspect of the invention.
Alternatively, said connecting member used is a fuse detachably connectable to said potential redundancy resistance connecting terminal and said intermediate connecting terminal on the external surface of said main body, according to the third aspect of the invention.
Alternatively, said connecting member used is a switch for switching between ON and OFF mounted between said potentially redundant resistance connecting terminal and said intermediate connecting terminal, according to the fourth aspect of the invention.